200 Gb/s per Channel Unrepeatered Transmission Over 520 km Terrestrial Fibers

This letter demonstrates unrepeatered real-time transmission of 200 Gb/s (5 bit per symbol modulation format, 56.8 GBaud) signal over terrestrial 520 km single-span fiber link. This was achieved using ultra low-loss fibers with large effective area, ROPAs with dedicated fibers, and distributed Raman amplifiers with co- and counter-propagating pumps.